Method of supplying a propulsion device with fuel

ABSTRACT

A propulsion system for a submarine includes an electric motor driving a propeller supplied with current from a fuel cell battery and a hydrocarbon burning engine. The fuel in the form of a hydroaromatic hydrocarbon or a mixture of such hydrocarbons is stored near the propulsion system. The hydroaromatic hydrocarbon is split to form hydrogen and the corresponding aromatic hydrocarbon. The hydrogen is supplied to the fuel cell and the hydroaromatic hydrocarbon is supplied as fuel to the other propulsion device.

United States Patent Von Krusenstierna 51 Aug. 15, 1972 METHOD OFSUPPLYING A PROPULSION DEVICE WITH FUEL Inventor: Otto VonKrusenstierna, Vasteras,

Sweden Assignee: Allmanna Svenska Elektriska Aktiebolaget, Vasteras,Sweden Filed: Oct. 3, 1969 Appl. No.: 863,505

Foreign Application Priority Data Oct. 9, 1968 Sweden ..13640/68 US. Cl..60/207, 60/205, 1 14/ 16 G Int. Cl. ..F23k 5/00, B63h l/OO Field ofSearch ..60/205, 206, 207, 218, 219, 60/208; 114/35 S, 16 R, 16 GReferences Cited UNITED STATES PATENTS 12/1963 Smith et al 149/109 3/1965 Smith et a1 ..60/206 1/1966 Mullen et a1 ..60/218 3,263,414 8/1966Herbst ..60/206 OTHER PUBLICATIONS Heffner et al., pp. 318- 325 and 330-331 of Fuel Cell Systems, Advances in Chemistry Series 47, AmericanChemical Society, Washington, DC, 1965 TK 2920 A5 1963/64] PrimaryExaminer-Benjamin R. Padgett Attorney-Jennings Bailey, Jr.

[57] ABSTRACT 5 Claims, 3 Drawing Figures Patented Aug. 15, 19723,683,622

IA'L'EYTOR OTTO v0/v KRUSENST ERNA fww g METHOD OF SUPPLYING APROPULSION DEVICE WITH FUEL BACKGROUND OF THE INVENTION 1. Field of theInvention The invention relates to propulsion devices for submarinesincluding an electric motor propulsion system for slow speed and ahydrocarbon-powered device for higher speeds.

2. The Prior Art Propulsion devices for submarines are known whichcomprise a propulsion system for low speed comprising an electric motorwhich is supplied with current from a fuel cell batteryrunning onhydrogen and oxygen and a driving system for high speed comprising asteam turbine which is supplied with over-heated steam developed in acombustion chamber by combustion of hydrogen and oxygen. The hydrogenand oxygen are stored in liquid form in fuel tanks in the submarine.

Disadvantages with the known propulsion device are the difficulties ofstoring the fuel and the military vulnerability due to the extremetemperature requirements. Also the great weight of the storage vesselsin comparison with the weight of the fuel in them is a disadvantage.

SUMMARY OF THE DISCLOSURE According to the invention it has been foundthat considerable advantages can be gained if the fuel is stored in theform of hydroaromatic hydrocarbons which split during operation of thepropulsion device into hydrogen which is supplied to the fuel cell asfuel and into the corresponding aromatic hydrocarbon which is suppliedto the combustion chamber of the steam turbine or the equivalent asfuel. The hydroaromatic hydrocarbons are liquid or solid at roomtemperature and can therefore be stored in simple and light fuel tanks.Further, it has been found that the aromatic hydrocarbon produced can becompletely consumed in the combustion chamber of the turbine or theequivalent. In this way an extremely compact fuel system is obtained forthe propulsion device from the fuel/energy point of view.

The invention thus relates to a method of supplying a propulsion devicewith fuel, comprising a first propulsion system comprising an electricmotor which is supplied with current from a fuel cell battery and asecond propulsion system comprising machinery with a combustion chamberfor combustion of a fuel, such as a combustion motor, a Stirling motor,a steam turbine or a gas turbine, characterized in that the fuel of thepropulsion device is stored near the propulsion device in the form of ahydroaromatic hydrocarbon or a mixture of at least two hydroaromatichydrocarbons which split during operation to form hydrogen and thecorresponding aromatic hydrocarbon(s), the hydrogen produced beingsupplied as fuel to the fuel cell and the aromatic hydrocarbon(s)produced being supplied as fuel to the machinery with the combustionchamber.

The propulsion device according to the present invention is alsosuitable for other purposes than submarines where a high energy: fuelratio is required, for example space-research vehicles.

The hydroaromatic hydrocarbon may consist, among other things, ofhexahydrobenzene C H (cyclohexane), decahydronaphthalene C I-I(decaline),

tetrahydronaphthalene C H (tetraline), dihydrobenzene C H(cyclohexadiene), tetrahydrobenzene C l-I (cyclohexene),

dihydronaphthalene C H and hexahydronaphthalene C H or mixtures of suchhydrocarbons. In certain cases even other hydroaromatic hydrocarbonshaving more benzene rings may be used. Hydroaromatic hydrocarbons areparticularly preferred which are liquid at room temperature, for examplehexahydrobenzene, decahydronaphthalene and tetrahydronaphthalene ormixtures of these hydrocarbons. I-Iexahydrobenzene is particularlypreferred since this substance produces the greatest quantity of energyper weight unit. Solid hydroaromatic hydrocarbons are also usable butthey should suitably be used with other hydrocarbons which, togetherwith the solid hydrocarbon, produce liquid mixtures.

The invention also relates to a means for carrying out the methoddescribed, comprising a propulsion device which comprises a firstpropulsion system consisting of an electric motor which is supplied withcurrent from a fuel cell battery and a second propulsion systemcomprising machinery with a combustion chamber for combustion of a fuelsuch as a combustion motor, a Stirling motor, a steam turbine or a gasturbine, characterized in that a reactor for splitting the hydroaromatichydrocarbons to hydrogen and the corresponding aromatic hydrocarbon isconnected to the propulsion device with a connection to the fuel cellfor the supply of hydrogen produced as fuel to the fuel cell and with aconnection to the combustion chamber in the machinery with combustionchamber for the supply of aromatic hydrocarbon produced to thecombustion chamber.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be furtherdescribed with reference to the accompanying drawings in which FIG. 1shows schematically a means for carrying out the method according to theinvention,

FIG. 2 shows schematically a fuel cell in the fuel cell battery of themeans and FIG. 3 shows schematically a common power transmission fromthe two propulsion systems in the propulsion device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, l0 designates a fuelcell battery driven by hydrogen gas and oxygen gas, which generateselectric energy in known manner. The fuel cell battery charges anaccumulator battery 12, for example a lead battery, through conduits 11.The accumulator battery is connected by conduits 13 to a DC motor 14which directly drives the propeller shaft 15 of a submarine. Since theDC motor is directly connected to the propeller shaft a low speed motorcan be used, which runs more quietly since there is no noisy gear in thepropulsion system. For low speed preferably only this fuel cell batteryis used with its accumulator and motor to provide the propulsion systemfor the submarine.

The propulsion device also includes a second propulsion systemcomprising machinery with a combustion chamber, in the example shown agas turbine 16 with a combustion chamber 17. The turbine is connected tothe propeller shaft over a gear 18 and a coupling 19. When the coupling19 is connected the turbine 16 and the DC motor 14 drive the propellershaft 15 simultaneously so that the highest driving power can beobtained. This is of course the case at high speed. During silentrunning the turbine 16 and gear 18 are complete ly disconnected with thehelp of the coupling 19.

The fuel for the propulsion device is stored in the tank 20 and consistsin the example of hexahydrobenzene C I'I (cyclohexane). It is ledthrough the conduit 21 to a heated reactor 22 containing a catalyst, forexample platinum, palladium or nickel. Hexahydrobenzene is split in thereactor at 200300 C to form hydrogen gas and benzene C H The mixture ofhydrogen gas and benzene is led through the conduit 23 to a cooler 24 inwhich the benzene condenses to a liquid while the hydrogen remains agas. The hydrogen gas is led from the cooler through the conduit 25 to afuel chamber in the fuel cell battery 10. Hydrogen gas which is notconsumed in the fuel cell battery is returned through the conduit 26 tothe cooler 24. The benzene is led through the conduit 27 to a storagetank 36 and from there to the combustion chamber 17 of the turbine.

The oxidant of the propulsion device is stored in the tank 28 andconsists in the example of liquid oxygen. The oxygen is led through aconduit 29 which penetrates the cooler 24 to the oxidant chamber in thefuel cell battery. From there unconsumed oxygen is led off through theconduit 30 by a circulation pump, not shown, to a point in the conduit29. The oxygen which is vaporized on its way to the fuel cell battery isused as coolant in the cooler 24. Oxygen is also led through the conduit31 to the combustion chamber 17 of the turbine where it reacts withbenzene at a high temperature, preferably 800l,000 C. The gaseousreaction products are led from the combustion chamber through a conduit32 to the turbine 16 and then to a condenser 33 in which the pressure iskept very low with the help of a vacuum pump 34 in known manner. Thecondensate is led off through the conduit 35.

Instead of oxygen, hydrogen peroxide, for example, may be used asoxidant. In this case both the fuel and the oxidant may be stored asliquids at normal pressure. The decomposition heat when the hydrogenperoxide splits to from oxygen and water, which can be done, forexample, with platinum as catalyst, can advantageously be used for thecatalytic splitting of the hydrogen gas from the hexahydrobenzene orother hydroaromatic hydrocarbon used.

Instead of the cooler 24 the separation of the hydrogen gas and benzenecan be done by means of a membrane which is only permeable to hydrogengas. This membrane may consist, for example, of palladiumsilver and issuitably arranged in the immediate vicinity of the reactor so that itobtains the required operating temperature in a simple manner. Thehydrogen gas is led from behind the membrane to the fuel cell, while thebenzene remains at the front of the membrane and is led to a smallercooler to be condensed and carried to the storage tank 36.

A fuel cell battery usually consists of a very large number of fuelelectrodes and oxidant electrodes stacked successively with spaces forfuel, oxidant and electrolyte between them. Part of such a fuel cellbattery is shown in FIG. 2. It contains the porous fuel electrodes 40consisting of, for example, nickel activated with platinum and theporous oxidant electrodes 41 consisting of, for example nickel activatedwith silver. The electrodes 40 are attached in the frames 42 and theelectrodes 41 in the frames 43. The frames may consist, for example, ofa thermosetting resin. The frames are held together by clamp means, notshown, in the stacking direction and may be sealed to each other, forexample by O-rings or by welded joints of thermosetting resin. Theelectrodes are connected by outer conductor rails, not shown, either inseries with each other or in parallel. The porous electrodes 40 formseparating walls between the fuel in the gas chamber 44 and theelectrolyte in the electrolyte chamber 45. In the same way the porouselectrodes 41 form separating walls between the oxidant in the gaschamber 46 and the electrolyte in the electrolyte chamber 45.

The fuel, that is the hydrogen gas, is led through the channel 47connected to the conduit 25, into the gas chamber 44 and is withdrawnthrough the channel 48 connected to the conduit 26. Oxidant, that isoxygen gas, is supplied through the channel 49 connected to the conduit29, to the gas chamber 46 and withdrawn through the channel 50 connectedto the conduit 30. The electrolyte, with the electrode material used inthe example for instance potassium hydrate, is supplied through thechannel 51 to the electrolyte chamber 45 and withdrawn through thechannel 52. The electrolyte thus flows in an outer circulation circuitwhich is not shown in FIG. 1. FIG. 3 shows a suitable way of arrangingthe power transmission from the first propulsion system with the DCmotor and the second propulsion system with the turbine. The motor 14comprises a stator and a rotor 61, The stator 60 is journalled by meansof bearings 62 directly on the propeller shaft 15. The rotor 61 issupported by a hollow shaft 63 which is also journalled on the propellershaft 15 by means of bearings 64. With the help of a coupling 65 therotor 61 can be connected to the shaft 15 or disconnected from it. If itis not desired to disconnect the motor 14 from the propeller shaft 15,the coupling 65 may be made permanent. As previously described, theturbine 16 is connected to the propeller shaft 15 over the gear 18 andcoupling 19. The propeller shaft can thus be driven either by the motor14 or the turbine 16, or by both simultaneously.

I claim:

1. Method of supplying a propulsion device with fuel, said propulsiondevice comprising a fuel cell battery and a first propulsion systemcomprising an electric motor which is supplied with current from saidfuel cell battery and a second propulsion system comprising machinerywith a combustion chamber for combustion of a hydrocarbon fuel, whichcomprises storing the fuel of the propulsion device near the propulsiondevice in the form of at least one hydroaromatic hydrocarbon, splittingsaid hydroaromatic hydrocarbon to form a mixture consisting essentiallyof hydrogen and the corresponding aromatic hydrocarbon, supplying thehydrogen produced as fuel to the fuel cell and supplying the aromatichydrocarbon produced as fuel to the machinery with the combustionchamber.

2. Method according to claim 1, in which hexahydrobenzene is thehydroaromatic hydrocarbon.

hydroaromatic hydrocarbon fuel consists essentially of a mixture of atleast two of the substances selected from the group consisting ofhexahydrobenzene, decahydronaphthalene and tetrahydronaphthalene.

2. Method according to claim 1, in which hexahydrobenzene is thehydroaromatic hydrocarbon.
 3. Method according to claim 1, in whichdecahydronaphthalene is the hydroaromatic hydrocarbon.
 4. Methodaccording to claim 1, in which tetrhydronaphthalene is the hydroaromatichydrocarbon.
 5. Method according to claim 1, in which the hydroaromatichydrocarbon fuel consists essentially of a mixture of at least two ofthe substances selected from the group consisting of hexahydrobenzene,decahydronaphthalene and tetrahydronaphthalene.